Re^3: Allocation of anonymous arrays

There different shades of pointless in this discussion. :)

you don't have to keep all $arefs after construction.

  DB<112> for $aref ( [1,2,3],[4,5,6],[7,8,9] ) { 
                      $lookup{$aref} = $aref; 
                      $hash{$aref}   = [ reverse @$aref ]; 
                      }
 => ""

  DB<113> \%hash
 => {
  "ARRAY(0xa547e40)" => [9, 8, 7],
  "ARRAY(0xa5c2e68)" => [6, 5, 4],
  "ARRAY(0xa5c3188)" => [3, 2, 1],
}

  DB<114> \%lookup
 => {
  "ARRAY(0xa547e40)" => [7, 8, 9],
  "ARRAY(0xa5c2e68)" => [4, 5, 6],
  "ARRAY(0xa5c3188)" => [1, 2, 3],
}

  DB<115> print "@{$lookup{$_}}\n" for keys %hash
7 8 9
4 5 6
1 2 3
[download]

Hiding all of this behind a tied hash should be feasible, (depending on implementation details of Tie::Hash , IAW when, where and how "stringization" happens )

Anyway I didn't try to find such implementations on CPAN.

One use case could be to implement sets of complex data structures including set operations

Cheers Rolf

( addicted to the Perl Programming Language)

updates

corrected link to Tie::Hash

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Re^4: Allocation of anonymous arrays by AnomalousMonk (Archbishop) on Feb 08, 2014 at 16:07 UTC
I would be more comfortable with a more familiar data structure organization. In addition to familiarity, I think it offers benefits when data elements are added/removed/mutated: as long as data element generation is encapsulated, there are no worries about construction and especially destruction. >perl -wMstrict -MData::Dump -le "my @data = map data_element($_), [1, 2, 3,], [4, 5, 6,], [7, 8, 9,], ; ;; sub data_element { return { forward => $_[0], backward => [ reverse @{ $_[0] } ] }; } ;; dd \@data; $data[2]{forward}[1] == $data[2]{backward}[1] or die 'Oops...'; ;; ;; use constant { FWD => 0, REV => 1, }; ;; sub data_element2 { return [ @{[]}[FWD, REV] = ($_[0], [ reverse @{$_[0]}]) ]; } ;; my @data2 = map data_element2($_), [ 8, 7, 6, ], [ 5, 4, 3, ], [ 2, 1, 0, ], ; dd \@data2; $data2[0][FWD][1] == $data2[0][REV][1] or die 'Oops2...'; " [ { backward => [3, 2, 1], forward => [1, 2, 3] }, { backward => [6, 5, 4], forward => [4, 5, 6] }, { backward => [9, 8, 7], forward => [7, 8, 9] }, ] [ [[8, 7, 6], [6, 7, 8]], [[5, 4, 3], [3, 4, 5]], [[2, 1, 0], [0, 1, 2]], ] [download]	[reply] [d/l]
Re^5: Allocation of anonymous arrays by LanX (Saint) on Feb 08, 2014 at 16:19 UTC
I agree about encapsulation, thats why I mentioned Tie::Hash after demonstrating the raw mechanics in a REPL. If tied or functional or OO or whatever interface... YMMV! :) Anyway we are again speculating about the OPs real intention, he just showed us enough to think it's pointless for most thinkable motivations. So pointless that Perl could/should warn about using literal arrays or hashes as keys... update tl;dr ... I just used a `reverse` in my example to avoid triviality with a minimal amount of code, it was a workaround not a goal. The general problem is to use complex data-structures as keys, see also Using hashes for set operations... for a similar discussion. Cheers Rolf ( addicted to the Perl Programming Language)	[reply] [d/l]